Rotary electric machines for vehicles, such as engine-driven alternators, need to have a high power output in order to achieve reduction in the idling engine speed of a vehicle as an environmental measure. They also need to be reduced in size and weight in order to implement weight reduction of a vehicle for improvement its fuel efficiency and reduction in the width of the engine compartment for finding room therein.
For meeting the needs, some types of alternators are designed such that each of multiphase windings of a stator is made up of a plurality of conductor segments inserted in slots of the stator. One end of each of the conductor segments projecting one of the slots is sequentially welded to the other end of a corresponding one of the conductor segments projecting a corresponding another one of the slots so that the sequentially joined conductor segments provide radially layered annular windings. The configuration of each of the multiphase windings allows high density of the multiphase windings and low resistance therein.
An example of some types of alternators set forth above is disclosed in Publication U.S. Pat. No. 5,936,326 corresponding to Japanese Unexamined Patent Publication No. 2000-69729.
On the other hand, foreign particles, such as dust particles, electrolyte components including salt-water components, car shampoo components, and the like, may enter the engine compartment of a vehicle in which an alternator is to be installed. It is necessary for the alternator installed in the engine compartment to keep its proper output characteristics even under such an environment.
Particularly, because an alternator for vehicles is designed to be cooled by a fan installed therein, cooling air generated by the fan may cause foreign particles, such as dust particles and/or electrolyte components, to likely enter the inside of the alternator together therewith. For this reason, it is important to reliably ensure environment resistance of the stator.